The present invention is a protective guard, intended for use with a punch press, drill press or other power tool. The guard is designed to prevent the operator of the machine from placing his hands or other objects into the work zone of the machine when he is either operating the machine or attempting to remove a work piece which has become jammed in the machine. In addition, the protective guard prevents fragmented segments of the work piece from striking the machine operator. Thus, the guard is a safety device for preventing injury to the operator.
Protective guards of this general type are well known, and a common feature of such known devices is a cage or other similar barrier which encircles the work zone of the machine, but which has an opening to permit insertion of the work piece. The principal function of such guards is to provide the operator with protection from injury while preserving sufficient visibility of the work zone to permit adequate control of the operation of the machine upon a work piece.
In order to make such guards commercially useful, it is necessary that they be easily attached to and removed from the machine and that the operator be able to quickly and accurately adjust the size and shape of the opening in order to accommodate work pieces of varied size and shape. The latter feature is of particular importance due to the requirements for conforming the size of the opening to the size of the work piece which have been set by regulations promulgated under the Occupational Safety and Health Act. In addition, the general size and structure of the guard itself should desirably be such as to permit the use of a wide range of sizes of work pieces without requiring the operator to devote substantial time to the adjustment of the guard, which, in turn, results in increased down time for the machine. Furthermore, the guard should perform each of these functions without posing hazards to the machine operator due to the structural configuration of the device itself. None of the known prior art devices have been able to meet these standards.
As noted, the common feature of the prior art devices is a cage or similar structure which serves as a barrier to the hand of the operator. It is this barrier which defines the work zone of the machine by enclosing the punch ram (or equivalent machine member), the die or base plate and a portion of the flat work bed of the machine. In these prior art devices the barrier is customarily formed by a series of either vetically- or horizontally-oriented rods or tines. The rods are, in turn, either held in place by a frame or attached to each other by a series of fasteners so that they alone form the barrier. In either form of the barrier, the rods are secured in such a fashion as to allow adjustment by either sliding or pivoting movement. In several of the prior art devices the barrier consists of two or more structurally independent panels, each of which is composed of such rods.
In most of the prior art devices, adjustment of the guard to accommodate work pieces of various sizes and shapes is accomplished by individually adjusting each pivoting or sliding rod so as to conform the size of the opening to the size of the work piece. In these prior art devices this adjustment often requires the operator to loosen the pin, screw or other fastener which secures each rod or tine, move the tine and then re-tighten the fastener. In order to make a precise and exact adjustment of the size of the opening, the operator often must repeat this process numerous times, thus wasting a great deal of otherwise productive machine time.
In addition to the loss of time caused by these adjustments, there is another disadvantage of those prior art devices in which individual rods or tines make up the barrier. When a number of individual tines are slid or pivoted so as to create an opening which will admit a work piece, the ends of these tines necessarily protrude from the safety device, either upwardly or outwardly. In both instances these protruding tine ends present a signficant risk of injury to the operator. While an operator is working at a machine equipped with such a safety device, his face and head are especially vulnerable to injury from these protruding tines.
Another deficiency of the prior art devices is that a substantial amount of time and effort is required to detach the guard from the machine to an extent sufficient to permit access to the die or other operative part of the machine. The amount of work involved in detaching and reattaching the guard increases the loss of time and money caused by longer set-up times and also increases the likelihood that, once removed, the safety device will not be re-attached to the machine.
The prior art devices are commonly mounted upon the machine by bolts and must, therefore, be completely detached from the machine whenever set-up for a new job is required. Some of the devices are, however, bolted to the machine by way of one or more hinges. While portions of the barrier may consequently swing away from the work area of the machine during the set-up period, there still must be considerable time and effort expended in order to release the additional bolts or other fasteners which permit the device to be pivoted on its hinges. Other means for attaching these prior art safety devices to machines have been devised, e.g., brackets; however, these too require the device to be totally removed from the machine during set-up.
Yet another deficiency of the prior devices is that, while in place on the machine, they do not permit the operator to insert work pieces which are shorter than the width of the entire protective barrier. Thus, the devices are useful only when work pieces are used which are as long or longer than the width of the box-like enclosure formed by the barrier.
In summary, the devices of the prior art are time-consuming to adjust, are time-consuming to remove and re-attach, are themselves a hazard to the operator and are limited as to the shortest work piece which they will accommodate.